Battery apparatus for controlling plural batteries and control method of plural batteries

ABSTRACT

Lower order control devices control plural battery cells configuring plural battery modules. An input terminal of the low order control device in the highest potential, an output terminal of the low order control device in the lowest potential, and a high order control device are connected by isolating units, photocouplers. Diodes which prevent a discharge current of the battery cells in the battery modules are disposed between the output terminal of the low order control device and the battery cells in the battery module on the low potential side. Terminals related to input/output of a signal are electrically connected without isolating among the plural low order control devices.

This application is a continuation of U.S. application Ser. No.10/810,674 filed Mar. 29, 2004, now U.S. Pat. No. 6,891,352, which is adivisional of U.S. application Ser. No. 10/079,423, filed Feb. 22, 2002,now U.S. Pat. No. 6,762,588, which claims priority to JapaneseApplication No. 2001-258859.

BACKGROUND OF THE INVENTION

The present invention relates to a battery apparatus for controllingplural high energy battery cells connected in series and its controlmethod, and more particularly to a battery apparatus which is suitablefor a low order control device which controls a battery module havingplural battery cells connected in series and a high order control devicefor giving instructions to plural low order control devices.

For example, Japanese Patent Laid-Open Publication No. 10-322925describes a conventional battery apparatus which is comprised of pluralbattery cells connected in series as a battery module, plural batterymodules being connected in series, and a low order control devicedisposed for each battery module, a command being sent from a high ordercontrol device to the low order control device. The low order controldevices monitor the states of the battery cells possessed by thecorresponding battery modules. The low order control devices disposed inthe same quantity as that of the battery modules are electricallyconnected in series via the battery modules, a signal is transmittedbetween the high order control device and the low order control devicesand between the low order control devices by an isolating unit such as aphotocoupler in a configuration that no affect is caused by a potentialdifference between the control devices.

The low order control device adjusts the capacity of the battery cellsas described in Japanese Patent Laid-Open Publication No. 2000-92732 forexample. The capacity adjustment means the reduction of a voltagedifference between the battery cells by having a resistor connected inparallel to the battery cells via a switch, and when the battery cellsmeasured by a voltage detection circuit have a high voltage, driving theswitch to partly discharge the amount of electricity stored.Particularly, a lithium-ion battery, which has amorphous carbon withhigh relevancy between an open-circuit voltage and a remaining capacityas an anode active material, can effectively equalize the capacity ofeach battery cell by reducing a voltage difference between the batterycells.

In recent years, there has been used an ultra capacitor which can storethe same amount of electricity as the secondary battery and has lessdegradation in service life as compared with the secondary battery. Theultra capacity adopts a method of equalizing the voltage between thecapacitor cells as described in Japanese Patent Laid-Open PublicationNo. 2001-37077 for example. This method provides a circuit whichconnects a switch in parallel to the capacitor cells to detect thevoltage of the capacitor and bypasses part of electricity to the switch.It is similar to the aforesaid Japanese Patent Laid-Open Publication No.2000-92732.

The low order control device detects a voltage of the battery cell orthe capacitor cell, and when the voltage is high, operates the switch toadjust the capacity. Meanwhile, the high order control device sends aninstruction signal to make the low order control device to adjust thecapacity. In Japanese Patent Laid-Open Publication No. 2000-92732, anopen-circuit voltage of each battery cell of the battery module ismeasured when the low order control device is activated, and themeasured value is transmitted to the high order control device. The highorder control device calculates a reference voltage value at the time ofcapacity adjustment from the value of open-circuit voltage obtained fromall the low order control devices and gives instructions to the loworder control devices again.

SUMMARY OF THE INVENTION

Problems to be remedied by the present invention are following three.First, it is a cost problem. The secondary battery and the ultracapacitor are expected to be used for a battery apparatus for theelectric car or the hybrid electric car, but it is demanded that theircosts are reduced for mass production. For the cost reduction of thebattery apparatus, it is necessary to reduce the cost of the batterycell or the capacitor cell itself and also to reduce the costs of theplural low order control devices. To achieve it, it is effective to havethe low order control devices as ICs (integrated circuits).

However, even when the low order control device is ICed, the isolatingunit such as a photocoupler used for the signal transmission between thehigh order control device and the low order control devices and betweenthe low order control devices remains as it is. For example, when alithium-ion battery is used, it is assumed that the battery cell has avoltage of 3.6V and 40 batteries are connected in series, this potentialdifference is 144V between the battery in the lowest potential and thebattery in the highest potential. In this example, if four battery cellsare grouped into each battery module, ten low order control devices areprovided, and the respective low order control devices are provided withabout two isolating units for input and output. Thus, a total of 20isolating units are necessary, and there is a disadvantage that thecontrol devices cost high.

Second, there is a problem of reliability. There is a possibility thatan external interference enters the instruction signal due to noiseproduced by an inverter device or the like which is connected as a loadon the battery apparatus. Therefore, there is a problem that thereliability of the signal transmission is decreased when instructionsare given from the high order control device to the low order controldevices because of the external interference.

Third, there is a problem of accuracy of detecting a voltage. The plurallow order control devices are provided with a voltage detection circuitand detect a voltage of the battery cells disposed in the correspondingbattery modules, but the battery voltage detection needs highly accurateperformance with merely an allowable error of several tens of mV. Alithium-ion battery, which uses amorphous carbon for the anode activematerial, has an obvious relation between the open-circuit voltage andthe remaining capacity as compared with another battery such as a nickelmetal hydride battery. But, it is said that even the lithium-ion batteryhas an allowable error of ±50 mV or less in voltage equalization for thecapacity adjustment. Conversion of a voltage of 50 mV is equivalent toabout 5% of the remaining capacity of the lithium-ion battery. Thehighest voltage of the lithium-ion battery is about 4.2V but theaforementioned 50 mV is 1.2% with respect to 4.2%, indicating that theaccuracy of voltage detection is very strict.

In order to achieve the highly accurate voltage detection, an A/Dconverter of ten-odd bits is generally used, but the accuracy of the A/Dconverter depends on the accuracy of a reference voltage source.

Therefore, the low order control device needs a highly accuratereference voltage source with an extremely small error (e.g., about ±25mV). Since each low order control device is connected to the batterymodule having a different potential, it is difficult to share the highlyaccurate reference voltage source with the plural low order controldevices. Specifically, to achieve the highly accurate voltage detection,there was a problem that the cost of the reference voltage sources whichare respectively provided for the plural low order control devicesbecame high.

A first object of the present invention is to provide a batteryapparatus which has a quantity of isolating units decreased and isprovided with low-cost control devices.

A second object of the invention is to provide a control method of abattery apparatus, which reduces the influence by external interferencessuch as noise and can make the signal transmission with improvedreliability.

A third object of the invention is to provide an inexpensive batteryapparatus which can achieve the highly accurate voltage detection.

(1) In order to achieve the first object, the invention is directed to abattery apparatus comprising plural battery modules connected in serieswhich have plural battery cells connected in series; plural low ordercontrol devices which are disposed in correspondence with the pluralbattery modules and control the plural battery cells configuring thebattery modules; and a high order control device which controls theplural low order control devices, wherein there are provided anisolating unit or a potential converting unit which connects the inputterminal of the low order control device in the highest potential amongthe plural low order control devices, the output terminal of the loworder control device in the lowest potential, and the high order controldevice; and an interruption element which is disposed between the outputterminal of the low order control device and the battery cells in thebattery module on a low potential side and prevents the dischargecurrent of the battery cells in the battery module; and terminalsrelated to the input and output of a signal are electrically connectedin a non-isolated state among the plural low order control devices.

By configuring as described above, the quantity of the isolating unitscan be reduced, and the low-cost control device can be obtained.

(2) In the item (1) above, it is preferable that the input terminal ofthe low order control device is electrically connected to the batterycell on a high potential side among the battery cells within the batterymodule being controlled by the low order control device.

(3) In the item (2) above, it is preferable that the plural low ordercontrol devices, the isolating unit or the potential conversion unitwhich is disposed on the low order control devices in the highest andlowest potentials, and the high order control device are mounted on thesame package, and power is supplied from the outside of the package tothe high order control device.

(4) To achieve the first object, the invention is directed to a controlmethod of battery cells which is provided with plural battery modulesconnected in series which have plural battery cells connected in series;plural low order control devices which are disposed in correspondencewith the plural battery modules and control the plural battery cellsconfiguring the battery modules; and a high order control device whichcontrols the plural low order control devices, wherein the high ordercontrol device compares a signal transmitted to the low order controldevice in the highest potential with a signal returning from the loworder control device in the lowest potential, and transmits the nextinstruction when it is determined to be normal.

The aforementioned method enables to improve the reliability by reducingan influence due to the external interference such as noise.

(5) In the item (4), it is preferable that the low order control devicedetects the states of the plural battery cells of the battery modulecontrolled by the low order control device, takes a logical add or alogical product of the state detection signal and an input signaltransmitted from the low order control device in a high potential, andoutputs the result to the low order control device in a low potential;and the high order control device determines a defect of the batteryapparatus according to the signal returning from the low order controldevice in the lowest potential.

(6) In the item (4), it is preferable that the low order control deviceperforms the capacity adjustment to discharge the remaining capacity ofthe battery cell when the voltage of the battery cells in the batterymodule is higher than a reference value, and the low order controldevice having completed the capacity adjustment gets into a sleep mode.

(7) To achieve the third object, the invention is directed to a batteryapparatus, comprising plural battery modules connected in series whichhave plural battery cells connected in series; plural low order controldevices which are disposed in correspondence with the plural batterymodules and control the plural battery cells configuring the batterymodules; and a high order control device which controls the plural loworder control devices, wherein there are provided a voltage detectingunit which detects a voltage of the plural battery cells within thebattery modules, and an error calibration terminal which calibrates anerror of the voltage detecting unit.

By configuring as described above, the highly accurate voltage detectioncan be achieved, and the cost reduction can also be achieved.

(8) In the item (7), it is preferable that the voltage detecting unit isan A/D converter, and the low order control device compensates an outputvalue by previously giving a digital value to the error calibrationterminal of the A/D converter.

(9) In the item (8), it is preferable that the A/D converter comprisesan integration unit which integrates a unit amount of electricityaccording to the number of pulses; a comparing unit which compares theintegral value of the integration unit with the voltage of the batterycell and stops the pulse; a counter unit which outputs the number ofpulses when the pulse is stopped by the comparing unit; and acompensation unit which compensates output of the counter unit accordingto the digital value given to the terminal for calibrating the error.

(10) In the item (9), it is preferable that the compensation unitchanges a counted value of the counter unit according to the digitalvalue given to the error calibration terminal to compensate an offset ofthe A/D conversion and changes a width of the pulse to compensate a gainof the A/D conversion.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing a general structure of a batteryapparatus according to one embodiment of the present invention;

FIG. 2 is a circuit diagram showing an internal structure of the loworder control device used for the battery apparatus according to oneembodiment of the invention;

FIG. 3 is a circuit diagram showing a first structure example of anoutput circuit 6 and an input circuit 4 used for the low order controldevice in the battery apparatus according to one embodiment of theinvention;

FIG. 4 is a circuit diagram showing a second structure example of theoutput circuit 6 and the input circuit 4 used for the low order controldevice in the battery apparatus according to one embodiment of theinvention;

FIG. 5 is a flow chart showing the contents of control of the batteryapparatus according to one embodiment of the invention;

FIG. 6 is a flow chart showing the contents of control to adjust thecapacity in the battery apparatus according to one embodiment of theinvention;

FIG. 7 is a circuit diagram showing a structure of an A/D converter usedin the battery apparatus according to one embodiment of the invention;

FIGS. 8A to 8D are timing charts of the A/D converter used in thebattery apparatus according to one embodiment of the invention;

FIG. 9 is a circuit diagram showing a structure of a first counter 9 anda second counter 10 in the A/D converter used in the battery apparatusaccording to one embodiment of the invention;

FIG. 10 is a truth table of the A/D converter used in the batteryapparatus according to one embodiment of the invention;

FIG. 11 is a circuit diagram showing a general structure of the batteryapparatus according to another embodiment of the present invention; and

FIGS. 12A to 12D are timing charts showing the contents of control ofthe battery apparatus according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The battery apparatus and its control method according to one embodimentof the invention will be described with reference to FIG. 1 to FIG. 10.

First, a general structure of the battery apparatus according to thisembodiment will be described with reference to FIG. 1.

FIG. 1 is a circuit diagram showing the general structure of the batteryapparatus according to one embodiment of the invention.

Electric cells VB1, VB2, . . . , VB12 which are secondary batteries aredivided into battery modules each of which has four battery cellsconnected in series. A secondary battery apparatus used for an electriccar or a hybrid electric car may be provided with tens to twenties ofbattery modules. But, this embodiment always has the same structure evenwhen many modules are connected in series, so that the example of FIG. 1shows a structure example having three battery modules connected inseries.

In the shown example, a first battery module in the highest potentialconsists of the battery cells VB1, . . . , VB4. Positive and negativeelectrodes of the respective battery cells VB1, . . . , VB4 areconnected to terminals T1, T3, T5, T7, T9 possessed by a first low ordercontrol device IC-1, respectively. A capacity adjustment circuitcomprised of a resistor R1 and a switching element S1 is providedbetween the positive and negative electrodes of the battery cell VB1. Acontrol signal is input from a terminal T2 of the low order controldevice IC-1 to a gate terminal of the switching element S1. Similarly,capacity adjustment circuits comprised of a resistor R2 and a switchingelement S2, a resistor R3 and a switching element S3, and a resistor R4and a switching element S4 are provided between the positive andnegative electrodes of the battery cell VB2, the battery cell VB3 andthe battery cell VB4, respectively. The gate terminals of the switchingelements S2, S3 and S4 input a control signal from terminals T4, T6, T8of the low order control device IC-1, respectively.

A second battery module in the middle potential is provided with thebattery cells VB5, . . . , VB8. Similar to the first battery module,positive and negative electrodes of battery cells VB5, . . . , VB8 arerespectively connected to terminals T1, T3, T5, T7, T9 possessed by asecond low order control device IC-2. The battery cells VB5, . . . , VB8are also provided with a capacity adjustment circuit, which has aresistor R5 and a switching element S5, a resistor R6 and a switchingelement S6, a resistor R7 and a switching element S7, and a resistor R8and a switching element S8 connected in series between the positive andnegative electrodes.

Similarly, a third battery module in the lowest potential is providedwith the battery cells VB9, . . . , VB12. Positive and negativeelectrodes of the battery cells VB9, . . . , VB12 are respectivelyconnected to terminals T1, T3, T5, T7, T9 possessed by a third low ordercontrol device IC-3. The battery cells VB9, . . . , VB12 are alsoprovided with a capacity adjustment circuit, which has a resistor R9 anda switching element S9, a resistor R10 and a switching element S10, aresistor R11 and a switching element S11, and a resistor R12 and aswitching element S12 connected in series between the positive andnegative electrodes. And, the respective switching elements are drivenby the third low order control device IC-3.

The internal structures, functions and peripheral parts of the low ordercontrol devices IC-1, IC-2, IC-3 will be described later with referenceto FIG. 2 and later figures.

Then, connected relations of the low order control devices IC-1, IC-2,IC-3 will be described.

As the battery cell VB4 and the battery cell VB5 are connected inseries, the first low order control device IC-1 and the second low ordercontrol device IC-2 are connected in series. Similarly, the second loworder control device IC-2 and the third low order control device IC-3are connected in series.

The high order control device MPU gives a command from the first loworder control device IC-1 to the third low order control device IC-3. Acontrol command output from the high order control device MPU isisolated by photocouplers F1, F2, F3 and transmitted to input terminalsIn-1, In-2, In-3 of the first low order control device IC-1. Lightreceiving side transistors of the photocouplers F1, F2, F3 arerespectively connected to resistors RF1, RF2, RF3. The resistors RF1,RF2, RF3 receive power from the positive electrode of the battery cellVB1. The first low order control device IC-1 outputs the signalstransmitted to the input terminals In-1, In-2, In-3 from outputterminals Out-1, Out-2, Out-3. The output terminal Out-1, the outputterminal Out-2 and the output terminal Out-3 are connected withoutelectrical isolation to input terminals In-1, In-2, In-3 possessed bythe second low order control device IC-2.

Similarly, the second low order control device IC-2 outputs the signalstransmitted to the input terminals In-1, In-2, In-3 from the outputterminals Out-1, Out-2, Out-3. The output terminals Out-1, Out-2, Out-3of the second low order control device IC-2 are connected withoutelectrical isolation to input terminals In-1, In-2, In-3 possessed bythe third low order control device IC-3.

The low order control device IC-3 in the lowest potential operatescorresponding transistors Tr1, Tr2, Tr3 by the signals output from theoutput terminals Out-1, Out-2, Out-3, and the respective transistorstransmit the signals to the high order control device MPU viaphotocouplers F4, F5, F6 to which the second low order control device isconnected.

Here, the light emitting sides of the photocouplers F4, F5, F6 areconnected to a reference voltage output terminal VDD of the low ordercontrol device IC-3 to receive an electric current from the referencevoltage output terminal VDD. Resistors RF4, RF5, RF6 disposed betweenthe light emitting sides of the photocouplers F4, F5, F6 and thetransistors Tr1, Tr2, Tr3 are used to adjust an electric current passingto the light emitting sides of the photocouplers F4, F5, F6.

The internal circuit of the low order control device IC-1 has thenegative electrode of the battery cell VB4 as a reference potential, andthis reference potential is indicated by GND-1. The internal circuits ofthe low order control device IC-2 and the low order control device IC-3have the negative electrodes of the battery cell VB8 and the batterycell VB12 as reference potentials, and these reference potentials areindicated by GND-2 and GND-3. The respective reference potentials GND-1,. . . , GND-3 are different ground terminals used for the correspondinglow order control devices IC-1, . . . , IC-3. Meanwhile, the ground inthe whole structure shown in FIG. 1 is assumed to be the negativeelectrode of a power supply Vcc for the high order control device MPU.The high order control device MPU and the low order control devicesIC-1, IC-3 are isolated by the photocouplers F1, . . . , F6, so that thenegative electrode of the Vcc is also isolated from the respectivereference potentials GND-1, . . . , GND-3.

The terminals and peripheral parts of the low order control devicesIC-1, . . . , IC-3 will be described with reference to FIG. 2, butdifferences among the respective control devices IC-1, . . . , IC-3 arepotentials of the terminals A1, . . . , A3 and terminals B1, B2 providedfor them. These terminals are to compensate an error in detecting avoltage to be described with reference to FIG. 7, and a digital value“1” or “0” is given from the low order control device IC-1 to theterminals A1, . . . , A3 and the terminals B1, B2 according to thevoltage detection error separately possessed by the low order controldevice IS-3. Here, “1” is a reference voltage VDD of the low ordercontrol device, and “0” indicates potentials of the grounds GND-1,GND-2, GND-3 of the respective low order control devices. Theaforementioned voltage detection error is different among the low ordercontrol devices IC-1, . . . , IC-3, so that the value “1” or “0m” of theterminals A1, . . . , A3 and the terminals B1, B2 is different among therespective low order control devices IC-1, . . . , IC-3 in the exampleof FIG. 1.

The high order control device MPU detects an electric current ofcharging and discharging passing to the battery module by an isolationtype current detector CT. To detect a total voltage value of the batterymodules connected in series, it is divided by resistors RV1, RV2. Here,the high order control device MPU and the respective battery modules areisolated from one another, so that the voltage divided by the resistorsRV1, RV2 is temporarily converted into a pulse signal by avoltage-frequency converter VF, and output of the VF is transmitted tothe high order control device MPU via a photocoupler F7. The high ordercontrol device MPU reads a total voltage of the battery modules from theoutput of the voltage-frequency converter VF obtained from thephotocoupler F7 and calculates an average remaining capacity of thethree battery modules based on the obtained value and the electriccurrent obtained from the current detector CT.

When the electric car or the hybrid electric car has tens to twenties ofbattery modules, a structure that the highest low order control deviceIC-1 and the lowest low order control device IC-3 are connected via thehigh order control device MPU and the photocouplers is the same as inFIG. 1. Remaining tens to twenties of the low order control deviceswhich are disposed in the same number as the battery modules areconnected without isolation with the output terminal of the low ordercontrol device having input terminals In-1, In-2, In-3 disposed for abattery module in a potential higher by one level and the input terminalof the low order control device having the output terminals Out-1,Out-2, Out-3 disposed for a battery module in a potential lower by onelevel in the same way as the low order control device IC-2 of FIG. 1.

In the illustrated example, seven photocouplers F1, . . . , F6, F7 areused as isolating units. A configuration consisting of three low ordercontrol devices IC-1, . . . , IC-3 is shown in the example of FIG. 1,but even when there are ten low order control devices, the number ofphotocouplers as the isolating units may be seven. Meanwhile, accordingto a conventional configuration, when each battery module is comprisedof four battery cells and provided with ten low order control devices,each of the low order control devices is provided with about twoisolating units for input and output. Thus, a total of 20 isolatingunits are necessary. Meanwhile, because seven photocouplers are alwaysenough in this embodiment, the number of isolating units can bedecreased to reduce the cost of the control devices.

Then, an internal structure of the low order control device used for thebattery apparatus according to this embodiment will be described withreference to FIG. 2.

FIG. 2 is a circuit diagram showing the internal structure of the loworder control device used for the battery apparatus according to oneembodiment of the present invention. FIG. 2 shows the structure of thelow order control device IC-1, and the other low order control devicesIC-2, IC-3 have the same structure. Like reference numerals are used toindicate like components to those shown in FIG. 1.

Switching element drive units Dr1, Dr2, Dr3, Dr4 are respectivelyconnected to control terminals of capacity adjustment switching elementsS1, S2, S3, S4 and drive the respective switching elements S1, S2, S3,S4. The drive units Dr1, Dr2, Dr3, Dr4 each obtain a signal from a logiccircuit 3 within the low order control device IC-1 and drive theswitching elements S1, . . . , S4 separately.

One end of analog switches AS1, AS2, AS3, AS4. is connected to thepositive electrodes of the battery cells and the other end commonlyconnected to a positive terminal C1P of a capacitor C1. Similarly,analog switches BS1, BS2, BS3, BS4 have their one end connected to thenegative electrodes of the battery cells and the other end commonlyconnected to a negative terminal C1N of the capacitor C1. And, an analogswitch CS1 is connected to the positive terminal C1P of the capacitor C1and the other end of the analog switch CS1 is connected to a positiveterminal C2P of a second capacitor C2. Besides, an analog switch CS2 isconnected to the negative terminal C1N of the capacitor C2 and the otherend of the analog switch CS2 is connected to the negative terminal C2Nof the second capacitor C2.

The analog switch AS1 and the analog switch BS1 are paired, and also AS2and BS2, AS3 and BS3, and AS4 and BS4 are paired respectively and turnedon or off at the same time. Pair (a) of the analog switch AS1 and theanalog switch BS1, pair (b) of the analog switch AS2 and the analogswitch BS2, pair (c) of the analog switch AS3 and the analog switch BS3,and pair (c) of the analog switch AS4 and the analog switch BS4 operateas four multiplexer switches. Specifically, one of the battery cellsVB1, . . . , VB4 is selected by the multiplexer switches of (a), . . . ,(d), and the selected battery cell is connected to the first capacitorCS1. Meanwhile, the analog switch CS1 and the analog switch CS2 areturned on or off simultaneously and, when they are turned on, the firstcapacitor CS1 and the second capacitor CS2 are connected.

It is assumed that the operation mode that the analog switch CS1 and theanalog switch CS2 are turned on is (e). And, for example, when thebattery cell VB1 is measured for a voltage, the logic circuit 3alternately repeats a first mode to turn on the pair (a) of the analogswitch ASI and the analog switch BS1 and a second mode to turn on thepair (e) of the analog switch CS1 and the analog switch CS2. During theabove operation, the multiplexer switches of (b), . . . , (d) are heldoff. The first mode (a) and the second mode (e) are pulse repeated forhundreds of times to finally have the same voltage among the batterycell VB1, the analog switch CS1, and the analog switch CS2. This isbecause when (a) and (b) are performed once, an electric currentcorresponding to a potential difference between the battery cell VB1 andthe analog switch CS1 and between the analog switch CS1 and the analogswitch CS2 flows, and a potential difference is reduced.

The first mode to turn on the pair (b) of the analog switch AS2 and theanalog switch BS2 and the second mode to turn on the pair (e) of theanalog switch CS1 and the analog switch CS2 are alternately repeated,during which the multiplexer switches of (a), (c) and (d) are held off,and the first mode (b) and the second mode (e) are pulse repeated forhundreds of times. As a result, the battery cell VB2, the analog switchCS1 and the analog switch CS2 have the same voltage.

Similarly, the first mode to turn on the pair (c) of the analog switchAS3 and the analog switch BS3 and the second mode to turn on the pair(e) of the analog switch CS1 and the analog switch CS2 are alternatelyrepeated. As a result, the battery cell VB3, the analog switch CS1 andthe analog switch CS2 have the same voltage.

And, the first mode to turn on the pair (d) of the analog switch AS4 andthe analog switch BS4 and the second mode to turn on the pair (e) of theanalog switch CS1 and the analog switch CS2 are alternately repeated. Asa result, the battery cell VB4, the analog switch CS1 and the analogswitch CS2 have the same voltage.

In the figure, the voltage detection circuit indicated by a broken linehas a structure including the aforementioned multiplexer switches,analog switches, and first and second capacitors. Output of the voltagedetection circuit 1 is a positive voltage (C2P) of the analog switchCS2. The positive voltage C2P is compared with the reference voltagecorresponding to an overcharge voltage, an overdischarge voltage, acapacity adjustment level or the like by comparators CMP1, CMP2, CMP3.The reference voltage is supplied from a reference power circuit 2. Theoutput (C2P) of the voltage detection circuit 1 is transmitted as adetected cell voltage Vx to input of an A/D converter 7, and the analogvalue of the positive voltage (C2P) is changed to a digital value by theA/D converter 7. The A/D converter 7 can compensate a voltage detectionerror by the signal given to the aforementioned terminals Al, . . . , A3and the terminals B1, B2.

The reference power circuit 2 produces a fixed voltage (e.g., 5 V) fromthe total voltage of the battery cells VB1 to VB4, supplies an electriccurrent to a reference voltage element VR which is disposed outside ofthe low order control device IC-1 to produce a very accurate voltagethan the previous constant voltage and takes the voltage from a terminalVref-1 into the low order control device IC-1. The voltage input fromthe terminal Vref-1 is divided into several kinds of voltages, which arethen used as the reference voltages according to the comparators CMP1,CMP2, CMP3. A clock generator 5 produces a clock by an oscillator CZdisposed outside of the low order control device IC-1 and uses it in thelogic circuit 3 or the like. Detailed structures of an input circuit 4and an output circuit 6 will be described later with reference to FIG. 3and FIG. 4.

Then, a first structure of the output circuit 6 and input circuit 4 usedfor the low order control device in the battery apparatus according tothe embodiment will be described with reference to FIG. 3.

FIG. 3 is a circuit diagram showing the first structure of the outputcircuit 6 and the input circuit 4 used for the low order control devicein the battery apparatus according to one embodiment of the invention.FIG. 3 shows details of the output circuit 6 of the low order controldevice IC-1 and the input circuit 4 of the low order control deviceIC-2. Like reference numerals are used to indicate like components tothose shown in FIG. 1 and FIG. 2.

A transistor Q in a power circuit 2 has a base electric currentcontrolled by a power control circuit 8 to output a fixed voltage to aterminal VDD and supplies the fixed voltage to the output circuit 6.

The output circuit 6 is disposed between the terminal VDD and the GND-1of the low order control device IC-1 and has a complementary switchcomprised of P-MOSFET (MP1) and N-MOSFET (MN1). A resistor R14 isconnected between the P-MOSFET (MP1) and the N-MOSFET (MN1). And, theP-MOSFET (MP1) is connected with a resistor R13 in parallel. Output ofthe complementary switch is applied to a gate terminal of P-MOSFET(MP3).

Here, when the P-MOSFET (MP1) is turned on by a signal output from thelogic circuit 3, a short-circuit is caused between the gate and thesource of the P-MOSFET (MP3) to turn off the P-MOSFET (MP3). And, whenthe N-MOSFET (MN1) is turned on, voltages which are resulted from thedivision of the voltage of the terminal VDD by the resistor R13 and theresistor R14, and voltages at both ends of the resistor R13 are appliedbetween the gate and the source of the P-MOSFET (MP3). The voltages atboth ends of the resistor R13 are set to be larger than a gate thresholdvoltage of the P-MOSFET (MP3) and turn on the P-MOSFET (MP3) but set tobe slightly larger than a gate threshold voltage to suppress an outputelectric current of the P-MOSFET (MP3) (about 1V or 2V higher than athreshold voltage).

As a result, the P-MOSFET (MP3) operates as a fixed current switch andpasses the output fixed electric current to the input circuit 4 of thelow order control device IC-2. An electrostatic breakdown preventioncircuit which has a diode D1 and a resistor RE1 connected in series isdisposed between the output terminal of the P-MOSFET (MP) and theterminal VDD, and when a serge voltage is input from the outside to theoutput terminal Out-1, the serge voltage is bypassed to the terminal VDDand a capacitor CV1 connected to the terminal VDD via the resistor RE1and the diode D1.

Thus, the electrostatic breakdown between the gate and the source of theP-MOSFET (MP3) due to the serge voltage can be prevented. And, aresistor RE2 and a diode D2 are also provided between the outputterminal and GND-1 of the P-MOSFET (MP3) as measures for anelectrostatic breakdown, and a zener diode ZD1 is additionally connectedin series.

As shown in the drawing, when I/O terminals of the two low order controldevices IC-1, IC-2 are connected without isolating, an electric currentpath, which starts from the output terminal Out-1 and returns to GND-1via the input terminal In-1 and the battery cell connected to the loworder control device IC-2, is formed when P-MOSFET (MP3) is off, and thebattery cell is discharged. When the state is left as it is, the batterycell is overdischarged. Therefore, the zener diode ZD1 having abreakdown voltage higher than the battery cell voltage is disposed onthe above electric current path to interrupt the discharge current.

Then, the structure of the input circuit 4 will be described. The inputterminal In-1 of the low order control device IC-2 is connected to thenegative electrode of the battery cell VB5 through the series connectionof a resistor RE4 and a resistor RE6. Therefore, the reference potentialof the input terminal In-1 is a negative potential of the battery cellVB5 higher than GND-2. The gate terminal of N-MOSFET (MN2) is connectedto the input terminal In-1 via a resistor RE3, and the source terminalof N-MOSFET (MN2) is also connected to the negative electrode of thebattery cell VB5 via the resistor RE6. A diode D3 is disposed betweenthe gate terminal of the N-MOSFET (MN2) and the positive electrode ofthe battery cell VB5, and a diode D4 is disposed between the gateterminal and the source terminal of the N-MOSFET (MN2) in order toprevent an electrostatic breakdown. By configuring in this way, theN-MOSFET (MN2) has a reference potential which becomes a negativepotential of the battery cell VB5 higher than the GND-2.

A resistor RE5 is disposed between the drain terminal of the N-MOSFET(MN2) and the positive electrode of the battery cell VB5, and voltagesat both ends of the resistor 5 are applied between the gate and thesource of the P-MOSFET (MP4). The drain terminal of the P-MOSFET (MN4)is connected to GND-2 through the series connection of resistors RE7,RE8. And, a zener diode ZD2 is disposed in parallel to the resistor RE8,and voltages at both ends of the resistor RE8 are transmitted to thelogic circuit 3.

The input circuit 4 configured as described above is a circuit whichconverts a potential in the multiple steps. Specifically, a fixedelectric current output by the P-MOSFET (MP3) of the low order controldevice IC-1 is received by the N-MOSFET (MN2) which has the negativeelectrode of the battery cell VB5 as the potential reference, and whenthe N-MOSFET (MN2) is turned on, the P-MOSFET (MP4) is turned on with avoltage produced in the resistor RE5, and a signal voltage is producedat both ends of the resistor RE8 with an electric current passingthrough the P-MOSFET (MP4) and transmitted to the logic circuit.

A general circuit, particularly an integrated circuit, has an inputterminal with the ground as the reference potential and an outputterminal. Meanwhile, the low order control device of this embodiment hasoutput connected to a fixed electric current and input connected to areference potential higher than the ground of the circuit and convertsthe potential in the multiple steps by the output circuit. Such aconfiguration is necessary to connect the control devices withoutisolating. The prevention of the discharge of the battery cell by thezener diode ZD1 was described above. And, when the potential standard ofthe input terminal In-1 is selected at the ground GND-2, the batterycells VB5, . . . , VB8 constitute a route which runs to discharge fromthe output terminal Out-1 of the low order control device IC-1 via theinput terminal In-1 of the low order control device IC-2 while theP-MOSFET (MP3) is off. In order to interrupt the discharge current, itis necessary to increase a breakdown voltage of the zener diode. And, asa voltage between the source and the drain of the P-MOSFET (MP3), atotal voltage of the battery cells VB5, . . . , VB8 is applied, so thata voltage stress is always applied to the P-MOSFET (MP3). In view of theabove points, it is desired that the reference potential of the inputterminal In-1 is selected to be high and the breakdown voltage of thezener diode ZD1 is set low so to reduce a voltage stress of the P-MOSFET(MP3).

As described above, the discharge current route is formed between theoutput terminal of the low order control device and the battery cells inthe battery module on the low potential side. Specifically, between theoutput terminal Out-1 of the low order control device IC-1 and thebattery cell VB6 in the battery module (comprised of the battery cellsVB5, VB6, VB7, VB8) on the potential side lower than the low ordercontrol device IC-1, there is formed a discharge current routeconnecting the output terminal Out-1 of the low order control deviceIC-1, input terminal In-1 of the low order control device IC-2, theresistor RE3, the diode D4, the positive electrode of the battery cellVB6, the negative electrode of the battery cell VB5, the positiveelectrode of the battery cell VB5, the ground GND-1 of the low ordercontrol device IC-1, the zener diode ZD1, the diode D2, the resistorRE2, and the output terminal Out-1 of the low order control device IC-1.Therefore, this embodiment has interception elements such as the zenerdiode ZD1, the diodes D2, D4 and the like disposed on this dischargecurrent route in order to prevent the discharge of the batteries.

Then, a second structure example of the output circuit 6 and the inputcircuit 4 used for the low order control device in the battery apparatusaccording to this embodiment will be described with reference to FIG. 4.

FIG. 4 is a circuit diagram showing the second structure example of theoutput circuit 6 and the input circuit 4 used for the low order controldevice in the battery apparatus according to one embodiment of theinvention. FIG. 3 shows the details of the output circuit 6 of the loworder control device IC-1 and the input circuit 4 of the low ordercontrol device IC-2. Like reference numerals are used to denote likecomponents to those shown in FIG. 1, FIG. 2 and FIG. 3.

The output circuit 6 of the low order control device IC-1 has the samestructure as the output circuit 6 shown in FIG. 3.

The input circuit 4 of the low order control device IC-2 is differentfrom the input circuit shown in FIG. 3 in the following points.Specifically, the source terminal of P-MOSFET (MP5) is connected to theinput terminal In-1, the gate terminal of the P-MOSFET (MP5) isconnected to the positive electrode of the battery cell VB5. Thus, thereference potential of the input terminal In-1 is selected for thepositive electrode voltage of the battery cell VB5 having the samepotential as the ground GND-1 of the low order control device IC-1.

The P-MOSFET (MP5) has zener diode ZD3 and resistor RE9 disposed betweenthe source and the gate, and the gate voltage is applied to the P-MOSFET(MP5) with the fixed electric current output by the P-MOSFET. (MP3) toturn on the P-MOSFET (MP5). The drain terminal of the P-MOSFET (MP5) isconnected to the negative electrode of the battery cell VB6 via theresistor R4 and the zener diode ZD4. Both end voltages of the resistorRE4 are applied as gate-to-source voltages of the N-MOSFET (MN2). Thesource terminal of the N-MOSFET (MN2) is also connected to the negativeelectrode of the battery cell VB6 via the zener diode ZD4. Resistor RE5is disposed between the drain terminal of the N-MOSFET (MN2) and thepositive electrode of the battery cell VB5 to apply both end voltages ofthe resistor RE5 between the gate and the source of the P-MOSFET (MP4).The drain terminal of the P-MOSFET (MP4) is connected to the groundGND-2 through the series connection of the resistors RE7, RE8. Zenerdiode ZD2 is disposed in parallel to the resistor RE8 to transmit bothend voltages of the resistor RE8 to the logic circuit 3.

According to the above configuration, there is no battery cell on theroute running from the output terminal Out-1 of the low order controldevice IC-1 to the ground GND-1 via the input terminal In-1 of the loworder control device IC-2 and the zener diode ZD3, and there is no needto worry about the discharge current of the battery. There is alsoformed a route running from the input terminal In-1 of the low ordercontrol device IC-2 to reach the negative electrode of the battery cellVB6 via the drain and the source of the P-MOSFET (MP5) and the zenerdiode ZD4 and returning to the ground GND-1 from the battery cell VB6and the battery cell VB5. When the P-MOSFET (MP3) is off, the P-MOSFET(MP5) is also off, and the battery cells VB5, VB6 do not discharge overthis route. A first element which cuts off the discharge current is theP-MOSFET (MP5), and the zener diode ZD4 is tediously used to cut off thedischarge current, when the P-MOSFET (MP5) is defective and flows thedischarge current.

As described above, by configuring as shown in FIG. 3 or FIG. 4, even ifthe input and output terminals of the low order control device areconnected without isolating, the discharge current of the battery cellcan be cut off, and the non-isolating connection can be made. In theexamples of FIG. 3 and FIG. 4, the output circuit of the low ordercontrol device IC-1 and the input circuit of the low order controldevice IC-2 are shown by one channel respectively, but they are providedwith the same structure in more than one for a single low order controldevice as shown in FIG. 1.

Then, a method of controlling the battery apparatus according to thisembodiment will be described with reference to FIG. 5. Here, contents ofcontrol to operate the low order control devices IC-1, . . . , IC3according to the instruction from the high order control device MPU inthe examples shown in FIG. 1 to FIG. 4 will be described.

FIG. 5 is a flow chart showing the contents of control of the batteryapparatus according to one embodiment of the invention.

Here, a flow to make a normal operation after the low order controldevices IC-1, . . . , IC-3, which have been in a sleep mode, areactivated by the signal from the high order control device MPU will bedescribed.

In step s1, the high order control device MPU transmits an activationsignal to the input terminal In-1 of the low order control device IC-1via the photocoupler F1.

Then, the input circuit 4 of the low order control device IC-1 convertsthe potential of the signal transmitted to the input terminal In-1 andtransmits the signal to the internal power supply circuit 2 in step s2.

Then, the internal power supply circuit 2 operates to control thetransistor Q in step s3. It takes time before external capacitor CVI ofthe low order control device IC-1 is recharged with the output currentof the transistor Q so to have a predetermined voltage VDD.

Then, when the voltage of the capacitor CV1 reaches a prescribed valueor higher which is slightly smaller than the voltage VDD in step s4, thelogic circuit 3 and also each circuit shown in FIG. 2 are operated.Then, the voltage of CV1 is controlled to the fixed value VDD.

Then, the logic circuit 3 recognizes the activation signal transmittedfrom the high order control device MPU and transmits it to the low ordercontrol device IC-2 having a potential lower by one rank through theoutput circuit 6 in step s5.

Similarly, the low order control device IC-2 and the low order controldevice IC-3 are operated by the same flow as in the steps s1, . . . ,s5. Besides, the low order control device IC-3 returns the activationsignal to the high order control device MPU via the photocoupler F4.

Then, the high order control device MPU recognizes that all the loworder control devices IC-1, IC-2, IC-3 are activated from their sleepmode and proceeds to give the next instructions in step s6.Specifically, the high order control device MPU uses photocouplers F1, .. . , F3 and transmits serial type control instructions to the low ordercontrol devices IC-1, . . . , IC-3.

Then, the low order control device IC-1 converts the potential of theserial signal obtained from the input terminals In-1, . . . , In-3 bythe input circuit 4 and deciphers by the logic circuit 3 in step s7.And, the signal is temporarily stored in the register, and the sameserial signal is sent to the next low order control device IC-2.

Subsequently, the low order control devices IC-2, IC-3 also operate inthe same way as in the step s7. And, the low order control device IC-3uses the photocouplers F4, . . . , F6 to return the serial signal to thehigh order control device MPU.

In step s8, the high order control device MPU checks the returned serialsignal and, if it is normal, sends the next control instructions.Meanwhile, if the 10 serial signal returned to the high order controldevice MPU had an error, the number of errors related to the signaltransmission is multiplied in step s9 and, if it is less than anallowable number of times, the same instruction signal is sent to thelow order control device IC-1 to perform once again. Meanwhile, if thenumber of errors has reached the allowable number of times or more, itis determined as abnormal, and the high order control device MPU outputsan abnormal signal to the high order system in step s10.

This control flow has a time delay before the instruction reaches fromthe low order control devices IC-1 to IC-3. However, a battery voltagechange is slower than the operation of the control circuit such as amicrocomputer, and the monitoring of the battery cell conditionperformed by the low order control devices IC-1 to IC-3 may besatisfactory by performing about every tens of ms. Therefore, a timedelay caused in the transmission of the signal from the low ordercontrol devices IC-1 to IC-3 is not a problem if it is smaller than thestate monitoring cycle. Meanwhile, the high order control device MPU cancompare the instruction issued to the low order control device IC-1 withthe one returned from the low order control device IC-3 to find which ofthe low order control devices had an error. Particularly, when a signalis sent without isolating, it is worried that there might be an effectdue to noise produced by an inverter or the like connected to thesecondary battery. But, according to the aforementioned control method,the high order control device MPU can check that each of theinstructions is accurately recognized by all the low order controldevices, and the reliability of the apparatus can be improved.

With reference to FIG. 6, the control method for the capacity adjustmentby the battery apparatus according to this embodiment will be described.

FIG. 6 is a flow chart showing the contents of control to adjust thecapacity of the battery apparatus according to one embodiment of thepresent invention.

The high order control device MPU instructs the adjustment of capacityto the low order control devices IC-1, IC-2, IC-3 in step s11.

Then, the low order control devices IC-1, IC-2, IC-3 store theinstructions in the register and send the same instructions to a loworder control device having a potential lower by one level in step s12.This method is the same as the one shown in FIG. 5.

Then, the high order control device MPU checks the instructions returnedfrom the low order control device IC-3 in step s13 and, if they werenormal, proceeds to step s14 but if had an error, returns to step s11and gives the same instructions again.

If they were normal in step s14, the high order control device MPU sendsinstructions to the low order control devices IC-1, . . . , IC-3 to gointo sleep mode after the capacity adjustment.

Then, the high order control device MPU checks the return of theinstructions and gets into the sleep mode in step s15. Then, the loworder control devices IC-1, . . . , IC-3 do not receive any instructionfrom the high order control device MPU and operate in a standalonestate, respectively.

Specifically, the low order control devices IC-1, . . . , IC-3sequentially detect the voltage of the battery cells placed in thecorresponding battery module by the voltage detecting circuit 1 of FIG.2 and compare the detected value with a judgment level (capacityadjusting reference voltage: a voltage output to the comparator CMP3 bythe reference voltage circuit 2 of FIG. 2) in step s16.

When the voltage of the battery cells is higher than the judgment level,the switching elements S1, . . . , S12 corresponding to the respectivebattery cells are turned on in step s17, and the process of step s16 isperformed again.

When the voltage of the battery cells becomes lower than the judgmentlevel, the low order control devices IC-1, . . . , IC-3 check that thevoltage of the battery cells placed in the corresponding battery moduleis lower than the judgment value, turn off the internal power supplysupply 2 disposed in the respective devices and get into the sleep modein step s18. In the standalone state, the sequence of falling into thesleep mode of the low order control devices IC-1, . . . , IC-3 connectedin series is not decided. Therefore, it is configured in such a way toprevent disadvantages that an excessive voltage is applied to the fixedcurrent switch MP3 and the battery cells are locally discharged in thenon-isolated connection of the input/output between the high and loworder devices as shown in FIG. 3 and FIG. 4.

In the above example, the capacity adjusting instructions use a capacityadjusting reference voltage which is previously given to the comparatorCMP3 of FIG. 2. But, any voltage instructed by the high order controldevice MPU can be used as a capacity instruction value by using the A/Dconverter shown in FIG. 7. In this case, the judgment level in step s16is any voltage instructed by the high order control device MPU. Thispoint will be described later with reference to FIG. 7.

Then, a structure and operation of the A/D converter used for thebattery apparatus according to this embodiment will be described withreference to FIG. 7 to FIG. 10. The A/D converter in this embodiment isprovided with a function to calibrate an error of the voltage detectingunit.

First, a general structure of the A/D converter used for the batteryapparatus according to 10 this embodiment will be described withreference to FIG. 7 and FIGS. 8A to 8D.

FIG. 7 is a circuit diagram showing a structure of the A/D converterused for the battery apparatus according to one embodiment of thepresent invention. FIG. 8A to FIG. 8D are timing charts of the A/Dconverter used for the battery apparatus according to one embodiment ofthe invention. Like reference numerals are used to indicate likecomponents parts to those shown in FIG. 1.

As shown in FIG. 1, the A/D converter 7 is provided with compensationterminals A1, . . . , A3 and compensation terminals B1, B2 forcompensation of a voltage detection error. Voltage (voltage of C2P) Vxdetected by the voltage detecting unit 1 shown in FIG. 2 is transmittedto the positive terminal of a comparator 14 via a switch unit Sx3.Meanwhile, electric current i of the fixed current unit 16 isaccumulated in a capacitor Ci via a switch unit Sx1 which is driven insynchronization with the switch unit Sx3. A total voltage of the voltageof the capacitor Ci and an adjustment voltage (Voffset) output by anamplifier 15 is applied to the negative terminal of the comparator 14and compared with the detected voltage Vx. The capacitor Ci, after thevoltage of the battery cell is measured once, is discharged by adischarge circuit of a switch unit Sx2, driven by a logic inverter 13and a resistor Ri. Specifically, when the switch unit Sx3 is turned onand the detected voltage Vx is transmitted to the positive terminal ofthe comparator 14, the capacitor Ci has a voltage of zero, and thevoltage at the negative terminal of the comparator 14 is equal to theadjustment voltage (Voffset). The switch unit Sx2 remains in the offstate from the time when the switch unit Sx1 and the switch unit Sx3 areturned on. Therefore, after the time when the switch unit Sx1 and theswitch unit Sx3 are turned on, the voltage of the capacitor Ci isintegrated with the electric current i to increase with time.

Output of the comparator 14 changes from “1” to “0” when a voltageresulting from a sum of the voltage of the capacitor Ci and theadjustment voltage (Voffset) is higher than the voltage Vx of theelectric current to be detected. The A/D converter 7 performsintegration type detection for measuring a duration in which the outputof the comparator 14 changes to “0” from the time when the switch unitSx1 and the switch unit Sx3 are turned on.

Using the adjustment voltage (Voffset) depends on the relation betweenthe battery remaining capacity and voltage. For example, a lithium-ionbattery using amorphous carbon has a battery cell voltage (open-circuitvoltage) of about 2.9 V when the remaining capacity is 0% and anopen-circuit voltage is about 4.1 V when the capacity is 100%. Forexample, the A/D converter 7 is demanded to be able to detect a 10voltage ranging from 2.9 V to 4.1 V accurately, but a voltage at a timewhen the remaining capacity is 0% or below is excluded from themeasurement. Therefore, a voltage (e.g., 2 V) when the remainingcapacity is 0% or less is selected as an adjustment voltage (Voffset) soto enable to detect a voltage which is equal to or higher than theadjustment voltage with high accuracy. Here, the adjustment voltage is avoltage which is obtained by dividing the value of the reference voltageVref shown in FIG. 2 by resistance Rx1, Rx2 and multiplying the obtainedvalue with the gain of the amplifier 15.

A duration from the time when the switch unit Sx1 and the switch unitSx3 are turned on to the time when output of the comparator 14 becomes 0is measured as follows. First, a clock pulse is frequency divided by thefirst counter 9. It is assumed that the clock pulse shown in FIG. 8D hasa frequency of 10 MHz and counted for 128 for example, and a signal of ahalf cycle shown in FIG. 8A is produced. The number of counts isdifferent depending on whether the compensation terminals A1, . . . , A3are “1” or “0”, and FIG. 8A to FIG. 8D show an example that compensationof ±3 pulses can be made with respect to the standard 128 pulses.Details of the compensation will be described later with reference toFIG. 9.

In FIG. 7, when output of the comparator 14 is 1, an AND circuit 11transmits the pulse which is frequency divided by the first counter 9 tothe next second counter 10. The second counter 10 counts the output ofthe first counter 9 until the output of the comparator 14 becomes 0 asshown in FIG. 8C. It is assumed that the voltage of the capacitor Ci notcontaining the adjustment voltage and falling in a range of 0 V, . . . ,3 V is a full scale, and the number of counts up to 3 V is 128 pulses.Features of the second counter 10 include that a shift register 12counts ±1 (or 2) for the result of the second counter 10 depending onthe state that the compensation terminals B1, B2 are “1” or “0” as shownin FIG. 8B. Output of the shift register 12 is digitally compared withthe capacity adjustment level transmitted from the high order controldevice MPU or used in the role of transmitting the output of the shiftregister 12 to the high order control device MPU.

Here, the compensation by the first counter 9 according to thecompensation terminals A1, . . . , A3 is to compensate the voltage valueof the capacitor Ci which is determined depending on the values of theconstant current i and the capacitor Ci and corresponds to the gaincompensation. Compensation of the second counter 10 by the compensationterminals B1, B2 is to compensate the adjustment voltage which is outputof the amplifier 15 and corresponds to the offset compensation.

When it is assumed that the clock frequency is 10 MHz, the number ofcounts by the first counter 9 is 128 and the number of counts by thesecond counter is 128 in full scale as described above, and it takestime of about 1.1 ms when the battery cell has a voltage of 4 V.Therefore, the number of counts by the first and second counters may bechanged depending on the desired accuracy of voltage detection andmeasurement time.

The compensation terminals A1, A2, A3, B1, B2 of the A/D converter 7 areprovided to calibrate the accuracy of the reference voltage source whichis separately provided for the low order control devices IC-1, . . . ,IC-3 which are connected in series. Therefore, errors of the fixedcurrent i, the capacitor Ci and the adjustment voltage (Voffset) arepreviously detected for each of the low order control devices IC-1, . .. , IC-3, and information “1” or “0” is given to the terminals A1, . . ., A3 and the terminals B1, B2 to compensate such errors. This “1” or “0”can be set by connecting the respective terminals to the VDD or theGND-1 as described above, and a special device such as a laser trimmerof resistance is not required.

Then, structures and operations of the first counter 9 and the secondcounter 10 in the A/D converter used for the battery apparatus accordingto this embodiment will be described with reference to FIG. 9 and FIG.10.

FIG. 9 is a circuit diagram showing the structures of the first counter9 and the second counter 10 in the A/D converter used for the batteryapparatus according to one embodiment of the invention. FIG. 10 is atruth table of the A/D converter used for the battery apparatusaccording to one embodiment of the invention. Like reference numeralsare used to indicate like component parts to those shown in FIG. 7.

The counters 9, 10 shown have a structure corresponding to 128 counts.The first counter 9 is provided with flip-flops M1, . . . , M7 andinputs output of the respective flip-flops to a compensation logic 18.The compensation logic 18 can change the cycle of the frequency divisionby ±3 pulses depending on the states of the compensation terminals A1, .. . , A3. The compensation logic 18 is the truth table shown in FIG. 10which is prepared in the form of a logical circuit or software. Thecycle that the flip-flops M1, . . . , M7 are cleared is variabledepending on the output of the compensation logic 18, and a pulse whichhas the cycle to the clearness as a half cycle is sent to the secondcounter 10 which is comprised of flip-flops N1, . . . , N7. The shiftregister 12 compensates the output of the flip-flops N1, . . . , N7 by±1 count (or 2 counts) depending on the states of the compensationterminals B1, B2 and outputs.

When it is assumed that a voltage range of the capacitor Ci, which isdetermined by the comparator 14, is 0, . . . , 3V (0, . . . , 5V involtage Vx) at full scale, ±1 count compensated by the shift register 12corresponds to ±23.4 mV. And, a pulse width (input pulse width of thesecond counter) which is compensated by the compensation logic 18 can becompensated by ±2% if it is ±3 pulses to 128 pulses.

The low order control devices IC-1, IC-2, IC-3 shown in FIG. 1 inspectthe accuracy of the voltage detecting unit before shipping of theproducts, and evaluate the voltage detection accuracy related to thereference voltage error possessed by the respective products. And, thecompensation terminals A1, . . . , A3 and B1, B2 are used for each loworder control device to calibrate so that the voltage detection accuracyfalls in the allowable range. Thus, it is not necessary to providehigh-cost high precision parts for the reference voltage to achieve bothhigh accuracy and low-cost of the device.

As described above, the quantity of isolating units can be reduced, anda low-cost control device can be provided according to this embodiment.

It is also possible to reduce an influence caused by disturbance such asnoise and to make the signal transmission with improved reliability.

Besides, the high accurate voltage detection can be achieved, and it ispossible to make cost reduction.

Then, the battery apparatus according to another embodiment of theinvention will be described with reference to FIG. 11.

FIG. 11 is a circuit diagram showing a general structure of the batteryapparatus according to another embodiment of the invention.

The battery apparatus according to this embodiment has low order controldevices IC-1, IC-2 and a high order control device housed in a chargerpackage 100. Electric cells VB1 to VB4 and battery cells VB5 to VB8which configure battery modules are housed in a battery module 101separate from the charger package 100.

Conventionally, mobile equipment has a control device (equivalent to thelow order control devices IC-1, IC-2) for detecting a trouble ofbatteries mounted in a battery module. Meanwhile, a nickel hydrogen orlithium battery used for hybrid electric cars is a high power typebattery which can discharge and recharge an electric current of several,. . . , tens of times of a rated electric current in a short time. Sucha high power type battery is expected to be applied for civilian use(e.g., power tools, cordless cleaners, etc.) other than automobiles. Forexample, a power tool is demanded to have a function to discharge anelectric current of about ten times of a battery rating and to rechargequickly with an electric current of several times of a rated current.When an electric current of about ten times of the battery rating isdischarged, the voltage detecting unit of the control device detects avoltage which is obtained by synthesizing an open-circuit voltage (avoltage when a load is not connected to the battery) related to theremaining capacity of the battery and a dropped portion of the voltagewhich is determined by the product of the internal resistance of thebattery and a large current. When the synthesized voltage drops to anoverdischarge level or less, it is determined as an overdischarge by thedetecting circuit, and the apparatus stops. But, the high power typebattery is free from any trouble in view of safety even if thesynthesized voltage drops to the overdischarge level or less in a shorttime. The power tool is required to have a battery light-weighted andcost reduced. Therefore, if there is no obstacle on safety, the controldevice (such as an IC) related to the protection of the battery isfitted on a charger separate from the battery module to monitor thebattery for its abnormality by only a simple temperature detecting unitsuch as a thermistor when the tool is being used, and if a temperaturearound the battery exceeds an allowable value, an electric current maybe shut off on the side of a battery load such as a motor. The abovebattery uses are taken into consideration in this embodiment.

In the example shown in FIG. 11, the battery module 101 accommodateseight battery cells connected in series. Within the charger 100, the twolow order control devices IC-1, IC-2 shown in FIG. 2 are disposed inseries. The peripheral equipment of the low order control devices IC-1,CI-2, namely a capacity adjusting switch, a resistor, a clock oscillatorand reference voltage parts, have the same structure as those shown inFIG. 1. Voltage detection compensating terminals A1, A2, A3, B1, B2 arealso the same as in FIG. 1.

A difference from FIG. 1 is a method of connecting the high ordercontrol device MPU and the low order control devices IC-1, IC-2, and anisolating photocoupler is not used but a potential conversion unit usinga switching element is provided in this embodiment. Specifically, thepotential conversion unit which transmits a signal from the high ordercontrol device MPU to the low order control device IC-1 on the highpotential side are provided with N-MOSFET (MN3), (MN4), (MN5) to which agate signal is input from the high order control device MPU. Theseswitch units are respectively connected to a series resistor comprisingthe resistors r1 and r2, the resistors r3 and r4, and the resistors r5and r6. Here, the resistors r1, r2, r3 have one end connected to thepositive electrode of the battery cell VB1 in the highest potential.Voltages of the resistors r1, r2, r3 are connected to gates of theP-MOSFET (MP6), (MP7), (MP8), and when the N-MOSFET (MN3), (MN4), MN5)are turned on or off, the P-MOSFET (MP6), (MP7), (MP8) are also turnedon or off accordingly. The drain terminals of the P-MOSFET (MP6), (MP7),(MP8) are coupled to the input terminals In-1, In-2, In-3 of the loworder control device IC-1, respectively.

Similarly, a unit for potential conversion of a signal returning fromthe low order control device IC-2 on the low potential side to the highorder control device MPU is provided with N-MOSFET (MN6), (MN7), (MN8)of which gates are respectively connected to the output terminals Out-1,Out-2, Out-3 of the low order control device IC-3, and resisters r7, r8,r9 are connected between the drain terminals of the N-MOSFET (MN6),(MN7), (MN8) and the positive electrode of a control power supply 21(Vcc). And, the voltages of the resistors r7, r8, r9 return to the highorder control device MPU. The high order control device MPU also sends asignal to a recharge controlling circuit. Specifically, a rechargingcircuit is formed of a power MOSFET (MN9) connected to a high voltagepower supply VDC, its driver circuit 22, a backflow diode DF connectedto the power MOSFET (MN9), and a choking coil LF of which one end isconnected to the power MOSFET (MN9). And, an electric current passingfrom the high voltage power supply VDC to the battery module 101 via thepower MOSFET (MN9) is monitored by a current sensor CT2. The highvoltage source VDC is produced by an AC/DC converter 23 which isconnected to a commercial AC power supply, and output of the VDC is usedto produce the control power supply 21 for the high order control deviceMPU by a DC/DC converter 24.

The respective electrodes of the battery cells placed in the batterymodule 101 and the corresponding low order control devices IC-1, IC-2 inthe charger 100 are connected via terminals a, . . . , i. The positiveand negative electrodes of the battery module 101 and the charger 100are connected to pass a charging current. The charger 100 controls thecharging current passing through the power MOSFET (MN9) by a signaloutput from the high order control device MPU. The low order controldevices IC-1, IC-2 perform the capacity adjustment, which was describedwith reference to FIG. 6, during or after the battery module 101 isrecharged. For the capacity adjustment while recharging, when thebattery module 101 and the charger 100 are connected, a voltage of eachbattery cell is measured by the A/D converters mounted on the low ordercontrol devices IC-1, IC-2, and the measured values are sequentiallysent to the high order control device MPU. The high order control deviceMPU calculates a capacity adjustment level from the voltage of eachbattery cell and transmits to the low order control devices IC-1, IC-2.Then, the low order control devices IC-1, IC-2 perform the capacityadjustment and the detection of overcharging while the charging currentflows. It is to be noted that the operation to get into sleep mode afterthe adjustment described in connection with step s18 of FIG. 6 isomitted.

As described above, a low-cost control device can be achieved bydecreasing a quantity of isolating units according to this embodiment.

The signal transmission of which reliability is improved can be attainedby reducing the influence by the external interference, such as noise.

Besides, the highly accurate voltage detection can be achieved, and thecost reduction can be made.

The method of controlling the battery apparatus according to anotherembodiment of the present invention will be described with reference toFIG. 12A to FIG. 12D.

FIGS. 12A to 12D are timing charts showing the contents of control inthe battery apparatus according to another embodiment of the invention.The structure of the battery apparatus used in this embodiment can beeither one shown in FIG. 1 and FIG. 11.

FIGS. 12A to 12D show a transmitting method of I/O data which is sentfrom the high order control device MPU to the low order control deviceIC-1 or among the low order control devices IC-1, IC-2, IC-3.

The high order control device MPU transmits the clock signal shown inFIG. 12A and input data (FIG. 12B) in synchronization with the clocksignal to the low order control device IC-1 in the highest potential.And, data input from the high potential side to the low potential sideis serial transmitted among the low order control devices IC-1, . . . ,IC-3. In other words, the low order control device which has receivedthe input clock and input data outputs the same signal with shifting byone clock as shown in FIGS. 12C, 12D.

Thus, signal delay time between the input and output of the signal canbe shortened. In FIGS. 12B and 12D, OV, UV and 50% OR indicated by thebroken line indicate overcharge, overdischarge and capacity adjustmentjudging bits. When the input data received from the high potential sidehigher by one level has information on the OV, UV and 50% OR, it isindicated by the solid line in FIG. 12, but if not, it is indicated bythe broken line. In the output data, 50% OR is indicated by the solidline, and it means that there was an battery cell exceeding the capacityadjustment level as the result of detecting the voltage of the batterycells (e.g., the battery cells VB1, . . . , VB4) to which the low ordercontrol device having received the input data corresponds. Thus, the loworder control device takes logical add (OR) of the data input about theovercharge, overdischarge and capacity adjustment judgment and thedetected result of the corresponding battery cells, and transmits theresult to the low order control device.

The high order control device MPU can check that at least one among allthe battery cells exceeds the judgment level if the returned data hadany flag of the OV, UV, 50% OR stood.

By having the aforementioned serial signal, when the plural low ordercontrol devices are connected without isolating, a signal transmissiondelay is short, and a fail safe type is provided by virtue of the ORform, and reliability is improved. When a logical product is usedinstead of the logical add, the variation in battery voltage can bepresumed from the analysis of a signal when recharging or discharging,and the capacity adjusting function can be operated according to thedetected result.

In the embodiments shown in FIG. 1 to FIGS. 12A to 12D, the batterycells VB1, . . . , VB12 are assumed to be the secondary batteries, butthey are not limitative and may be an ultra capacitor.

According to the present invention, a quantity of isolating units isdecreased, and the cost reduction of the control device can be made.

And, the influence by the external interference such as noise isreduced, and the signal transmission with reliability improved can berealized.

Besides, highly accurate voltage detection can be achieved, and the costreduction can be made.

It should be further understood by those skilled in the art that theforegoing description has been made on embodiments of the invention andthat various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and scope of theappended claims.

1. A battery apparatus, comprising: a battery unit which includes pluralbattery modules connected in series each having plural battery cellsconnected in series; and a control unit which controls the battery unit,wherein the control unit includes: plural low order control deviceswhich are provided in correspondence with the plural battery modules,respectively, each of the plural low order control devices controllingthe plural battery cells corresponding to one of the plural batterymodules; and a high order control device which controls the plural loworder control devices, wherein the plural low order control devices areelectrically connected in series, each of the plural low order controldevices being supplied with electric power from the corresponding one ofthe plural battery modules, and wherein the high order control device issupplied with electric power from a power supply different from theplural battery modules, the high order control device being connectedelectrically in series through an isolation unit with the plural loworder control devices electrically connected in series.
 2. A batteryapparatus according to claim 1, wherein a reference voltage of theplural low order control devices differs from a reference voltage of thehigh order control device.
 3. A battery apparatus according to claim 2,wherein each of the plural low order control devices is coupled to, asthe reference voltage of the plural low order control devices, anegative electrode of the battery cell having a lowest voltage among theplurality battery cells of the corresponding one of the plural batterymodules, and the high order control device is coupled to, as thereference voltage of the high order control device, a negative electrodeof the power supply.
 4. A battery apparatus according to claim 3,wherein the reference voltage sides of the plural low order controldevices are isolated from the reference voltage side of the plural highorder control device by the isolation units.
 5. A battery apparatusaccording to claim 1, wherein each of the plural low order controldevices includes plural circuits, and a reference voltage for operatingthe plural circuits, wherein the reference voltage for operating theplural circuits is generated from a total voltage of the battery cellsof the corresponding one of the plural battery modules.
 6. A batteryapparatus according to claim 3, wherein each of the plural low ordercontrol devices includes an interruption element for interrupting acurrent flowing through a current path which is formed between each ofthe plural low order control devices and the corresponding one of theplural battery modules on a lower potential side.
 7. A battery apparatusaccording to claim 3, wherein each of the plural low order controldevices includes: an output circuit for outputting a signal of aconstant current to the corresponding one of the plural battery moduleson a lower potential side, and an input circuit for receiving a signalof a constant current outputted from the corresponding one of the pluralbattery modules on a higher potential sides, wherein the input circuitis coupled to a reference voltage higher than the reference voltage ofthe each of the plural low order control devices, and converts apotential of the signal outputted from the output circuit in multiplesteps.
 8. A battery apparatus according to claim 3, wherein each of theplural low order control devices includes: an output circuit foroutputting a signal of a constant current to the corresponding one ofthe plural battery modules on a lower potential side, and an outputcircuit for receiving a signal of a constant current outputted from thecorresponding one of the plural battery modules on a higher potentialside, wherein the input circuit is coupled to a reference voltage higherthan the reference voltage of the each of the plural low order controldevices, and converts a potential of the signal outputted from theoutput circuit in multiple steps, and wherein the output circuitincludes an interruption element for interrupting a current flowingthrough a current path which is formed between each of the plural loworder control devices and the corresponding one of the plural batterymodules on a lower potential side.
 9. A battery apparatus according toclaim 3, wherein each of the plural low order control devices includes:an output circuit for outputting a signal of a constant current to thecorresponding one of the plural battery modules on a lower potentialside, and an input circuit for receiving a signal of a constant currentoutputted from the corresponding one of the plural battery modules on ahigher potential side, wherein the input circuit is coupled to areference voltage that is the same as the reference voltage of thecorresponding one of the plural low order control devices on the higherpotential side, and converts a potential of the signal outputted fromthe output circuit in multiple steps.
 10. A battery apparatus accordingto claim 3, wherein each of the plural low order control devicesincludes: an output circuit for outputting a signal of a constantcurrent to the corresponding one of the plural battery modules on alower potential side, and an input circuit for receiving a signal of aconstant current outputted from the corresponding one of the pluralbattery modules on a higher potential side, wherein the input circuit iscoupled to a reference voltage that is same as the reference voltage ofthe corresponding one of the plural low order control devices on thehigher potential side, and converts a potential of the signal outputtedfrom the output circuit in multiple steps, and wherein the outputcircuit includes an interruption element for interrupting a currentflowing through a current path which is formed between each of theplural low order control devices and the corresponding one of the pluralbattery modules on a lower potential side.
 11. A battery apparatusaccording to claim 1, wherein the isolation unit is a photocoupler. 12.A battery apparatus according to claim 1, further comprising: a batterypack housing the battery unit therein; and a charger which houses thecontrol unit therein and charges the battery pack, wherein each of thebattery pack and the charger has terminals, and wherein the plural loworder control devices are coupled to the corresponding plural batterymodules through the terminals, respectively, by coupling same polaritiesof the battery pack and the charger to each other to charge the batterypack by the charger.
 13. A battery apparatus according to claim 11,wherein the isolation unit is a potential conversion unit.